In a vehicle such as an automobile, a steering support member is arranged, for example, in a space partitioned with a dash panel and an instrument panel. The dash panel is a vehicle body panel that is located in a vehicle front portion and delimits an engine room from a vehicle compartment. The instrument panel is an interior component arranged on a compartment side of the dash panel.
The steering support member is a member that extends in a vehicle width direction and both ends of which are fixed to the lateral sides of the vehicle such as dash side panels, and that supports various kinds of components such as a steering mechanism. Therefore, strength and rigidity to support the weight of various kinds of components is required for the steering support member. “Steering mechanism” refers to components including a steering shaft, a steering wheel and the like.
If the rigidity of the steering support member is low, vibrations from the vehicle body (e.g., the suspension) or engine vibrations when idling are transmitted to the steering mechanism, and the so-called steering vibrations that make occupants feel uncomfortable may occur.
In recent years, there is a tendency to strive for weight reduction vehicles. Therefore, the use of materials that have excellent specific strength and specific rigidity, that is, light alloys for which magnesium alloy is a typical example and resin composite materials for which carbon fiber reinforced plastics (CFRP) are a typical example to make vehicle components is attracting attention.
Because these materials also have excellent moldability, they are expected to be used as materials for steering support members. Existing steering support members are, for example, made of iron and have the shape of a round bar.
On the other hand, an instrument panel support structure made of magnesium, which supports a control column (corresponding to a steering mechanism or the like), is described in Japanese Translation of PCT International Application Publication No. JP 2007-506610. A driver's seat side member molded in one piece of a magnesium alloy, which supports a steering mechanism, is described in Japanese Patent Laid-open Publication No. JP 2006-160019.
Because materials with excellent moldability are used for the structures or members described in Japanese Translation of PCT International Application Publication No. JP 2007-506610 and Japanese Patent Laid-open Publication No. JP 2006-160019, a longitudinal section of the steering support member along a vehicle front-rear direction has a U shape in which one side (e.g., a vehicle front side) is open, for example, to enhance the rigidity thereof or not to damage other surrounding components.
Sufficient strength and rigidity on the open side of the steering support member may not be obtained if a longitudinal section thereof has a U shape. To prevent this situation, it is conceivable to increase a wall thickness or to add other reinforcing components. However, this will make the steering support member heavy and make it difficult to reduce its weight.
In view of the foregoing problem, it is an object of the present invention to provide a steering support member that can achieve enhanced support strength and support rigidity while reducing the weight thereof.